There has been known a cap mechanism formed by coupling a vessel body and a cover with a hinge and setting an elastic material inside the hinge so that, when the cover is closed, energy is stored in the elastic body. When a cover-opening claw based on the pushing system is operated, locking is released and the cover automatically opens due to the restoring force stored in the elastic material.
U.S. Pat. No. 4,711,360 discloses a mechanism provided by an elastic body set in and projecting from a vessel body. This elastic body is bent when the cover is closed, and when locking is released, the cover automatically opens due to the restoring force of the elastic body. However, the locking mechanism for the cover described in U.S. Pat. No. 4,711,360 is not clear.
U.S. Pat. No. 5,962,216 discloses a configuration in which elastic members are placed in a vessel body as well as a hinge section of a hinge cap, and when the cover is closed, the elastic members are compressed, and when locking is released, the cover automatically opened due to the restoring force of the elastic members. In the configuration of U.S. Pat. No. 5,962,216, however, the lock mechanism between the cover and the vessel body is a conventional one, and there is not any specific contrivance.
In Japanese Patent Laid-Open Publication No. 2002-211615 a typical automatic operation of a cap is enabled by operating a button. However, a plate member for operation is provided on an upper surface of the cap body, and once the cap cover is opened, the plate member or the structure around the plate member is in full view, so that the appearance is not good. According to Japanese Patent Laid-Open Publication No. 2002-211615, the cap body 2 has the deck panel section 10 for preventing the content from leaking in the movable section to deteriorate the smooth movement of the cap, and further most of the portion of the operating member 5 for transferring a pushing-in and opening drive force to the inside of the hinge 4 is hidden even when the cap cover 3 is opened, so that the appearance is improved and the content hardly infiltrates into the movable section of the operating member 5, so that the smoothness of the movement is not lost. With the invention of Japanese Patent Laid-Open Publication No. 2002-211615, however, there is not any specific contrivance for a locking mechanism for the cover.
Japanese Patent Laid-Open Publication No. H7-291326 improves the smoothness in an operation for opening a cap based on the so-called three-point hinge system. With this, the cover body 20 for opening and closing an outlet port is rotatably provided with the first hinge 31 in the cap body 10 having the outlet port. The substantially house shoe-shaped band plate 40 is provided between the cap body 10 and the cover body 20. The band plate 40 functions as a plate spring with one edge thereof rotatably attached via the second hinge 32 to the cap body 10 and further with the other edge of the band plate 40 rotatably attached via the third hinge 33 to the cover body 20. A hooking projection for engagement when fully closed is provided in a front edge section of the cap body as well as in a front edge section of the cover body 20, and a rotation center of the third hinge 33 when fully opened is set to be at the outer side of a virtual line C passing through a rotation center of the first hinge 31 and that of the second hinge 32.
However, also in the invention of Japanese Patent Laid-Open Publication No. H7-291326 there is not any specific contrivance for the engagement mechanism of the cap.
Japanese Utility Model Registration No. 3091998 has an object of the disclosed device to provide a self-opening hinge cap which can be produced with low cost. In the configuration, the cover is monolithically formed via the hinges 3, 3a on the cap body 1 using a molding die for injection molding. The cap body 1 and the cover 2 are coupled to each other at the positions of the hinges 3, 3a with an elastic opening member 4, and with the compressing action of this elastic opening member 4, the cover 2 is automatically opened around the hinges 3, 3a. Also the elastic opening member 4 is monolithically molded (by means of two-color injection molding) using a molding die for injection molding when the cover 2 is molded.
Also in the device of Japanese Utility Model Registration No. 3091998, there is not any particular contrivance for the locking mechanism for the cap.